1. Field of the Invention
The present invention relates to a process for converting propylene over MCM-22 zeolite catalyst to provide higher molecular weight hydrocarbons, particularly C6, C9 and C12 olefins. More particularly the conversion is carried out simultaneously with distillation in a distillation column reactor.
2. Related Information
In the present state of the art the catalysts are used in tubular reactors at severe conditions, i.e., 330-482° F. and 1000 to 1215 psig pressures. Prior catalysts which have been used for the oligomerization of propylene include supported phosphoric acid (sPa), metal complexes (U.S. Pat. Nos. 5,510,555; 4,695,664 and 6,501,001) and various zeolites, especially ZSM-22 and ZSM-57 (U.S. Pat. No. 6,143,942). These reaction systems have undesirable qualities characterized as one or more of: severe reaction conditions, short catalyst life and poor selectivity.
The reaction requires high temperature (330-482° F.) and high pressure (1000 to 1215 psig). The sPa system has a life of less than 1000 tons of product per ton of catalyst and then must be removed and discarded. The zeolites have shown increased life, e.g., 1500 to 3000 tons of product per ton of catalyst, but lose activity and must be regenerated at considerable expense. U.S. Pat. No. 6,072,093 teaches that the catalyst life may be extended by recycling cycloparaffins through the tubular reactor, which requires additional separation and recycling apparatus and an inventory of the non associated cycloparaffins. The metal complexes are homogeneous catalysts wherein the catalyst and the products must be separated with continuous catalyst makeup required. The selectivity of the sPa is toward the C9 and heavier while the preferred oligomers are the C6 and C9 which are converted to alcohols. The selectivities of the zeolites and metal complexes are somewhat better.
U.S. Pat. No. 4,956,514 discloses zeolite MCM-22 which has been shown to have favorable characteristics for the oligomerization of propylene at lower pressures and temperatures than the other catalyst.
U.S. Pat. No. 4,242,430 discloses the dimerization of isobutylene in a distillation column reactor using an acidic cation exchange resin as the catalyst which avoided the formation of higher oligomers.